the selection box (focus) moves slowly

Steps to Reproduce

1. import the attached file with larger visible rows and columns like:

    <spreadsheet id="ss" height="100%" width="100%" 
                 maxVisibleRows="2050" maxVisibleColumns="400" showContextMenu="true"
                 showToolbar="true" showSheetbar="true" showSheetTabContextMenu="true" showFormulabar="true"/>

2. visit the page with Chrome
3. scroll down to 900 row, scroll right to column AJ
4. keep pressing right key to move the focus (selection box)

Current Result

the selection box jumps over several cells when moving right. it doesn't appear on each cell on the row. watch the video.

• focusJump.mov
• focusJump-t10989.mp4

Expected Result

no such jump

Debug Information

• if I don't scroll down and right, just move focus right after importing. Such jumping is not obvious.
• check moveFocusHeavy.json.zip